The Cell Culture Core supplies high quality cells for the Program Project investigators. The facility is maintained such that it meets and exceeds the relevant federal health and safety standards. The majority of cells provided by the facility are foreskin-derived normal human keratinocytes. These cells are plated with media, conditions, density etc. as required by each program project investigator. Presently the facility is providing over 250 million cells per week to investigators, but it can produce greater than or equal to 500 million per week on demand. In addition, the facility has a large library of transformed and genetically altered lines that are available to investigators. The most frequently used by the investigators are the squamous cell carcinoma lines (SCC-4, SCC-12F2, SCC-12B2); and low passage cells (HaCaT, A431). These are maintained at low levels which allows for rapid boosting of cell numbers at the investigator's request. Dr. Mary L. Williams, Director, & Ms. Sally Pennypacker, Heady Technician, not only provide in vitro culture knowledge and expertise for other investigators, but also insure that health and safety inspections are passed; hoods and incubators are tested and serviced regularly; and that cultures are tested monthly for mycoplasma. Both Dr. Williams & Ms. Pennypacker also possess expertise in culturing basal cell carcinoma cells, adult skin keratinocytes and fibroblasts, fetal skin keratinocytes, late passage keratinocytes, fetal mouse skin keratinocytes; newborn and adult mouse keratinocytes; lifted keratinocyte cultures; and proficiency in explant methods. Core A also is developing fibroblast-free fetal keratinocytes, and optimizing both BCC isolation and late-passage keratinocyte cultures (i.e., greater pass 25). A fundamental part of the operation of Core A is the interaction between its personnel and members of the Program Project, allowing researchers to obtain high-quality cultures specifically tailored to their needs, while providing direct feedback for optimizing of techniques and protocols. The facility is now equipped with amber lights for work with light-sensitive compounds (e.g., retinoids, vitamin D and derivatives). Finally, Core A provides both maximum numbers of high quality cells and advice on in vitro methods to investigators, who rely heavily on this facility. The continued production of healthy keratinocytes will remain the priority of this key facility.